The fate of terrestrial organic matter in two Scottish sea lochs

Loh, Pei Sun; Reeves, Andrew; Harvey, S. M.; Overnell, Julian; Miller, Axel E. J.

doi:10.1016/j.ecss.2007.07.023

Cited by 32 publications

(25 citation statements)

References 79 publications

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“…This aligns well with previous OC measurements of 4.9 % in surface sediments of Airds Bay (Loh et al 2008b). The sedimentation rate in central Airds Bay has been assessed previously using a profile of excess 210 Pb and estimated to equal 0.59 cm year -1 (Overnell 2002).…”

Section: Benthic Carbon and Nutrient Turnover In A Highly Irrigated Csupporting

confidence: 81%

“…This implies that, on a scale of the chamber enclosed area (900 cm 2 ), the reduced equivalents that are being released during anaerobic degradation are being balanced by a concurrent oxidation by O 2 , and that O 2 consumption is a good proxy for the total benthic carbon mineralization rate, also in these sediments. The benthic mineralization in Scottish lochs is being sustained partly by local pelagic primary production and partly by terrestrially produced material that is supplied by riverine run-off (Loh et al 2008b(Loh et al , 2010. To our knowledge, there are no recent assessments of primary production or sedimentation for Loch Etive.…”

Section: Benthic Carbon and Nutrient Turnover In A Highly Irrigated Cmentioning

confidence: 99%

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Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

et al. 2016

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Based on in situ microprofiles, chamber incubations and eddy covariance measurements, we investigated the benthic carbon mineralization and nutrient regeneration in a *65-m-deep sedimentation basin of Loch Etive, UK. The sediment hosted a considerable amount of infauna that was dominated by the brittle star A. filiformis. The numerous burrows were intensively irrigated enhancing the benthic in situ O 2 uptake by *50 %, and inducing highly variable redox conditions and O 2 distribution in the surface sediment as also documented by complementary laboratory-based planar optode measurements. The average benthic O 2 exchange as derived by chamber incubations and the eddy covariance approach were similar (14.9 ± 2.5 and 13.1 ± 9.0 mmol m -2 day -1 ) providing confidence in the two measuring approaches. Moreover, the non-invasive eddy approach revealed a flow-dependent benthic O 2 flux that was partly ascribed to enhanced ventilation of infauna burrows during periods of elevated flow rates. The ratio in exchange rates of RCO 2 and O 2 was close to unity, confirming that the O 2 uptake was a good proxy for the benthic carbon mineralization in this setting. The infauna activity resulted in highly dynamic redox conditions that presumably facilitated an efficient degradation of both terrestrial and marine-derived organic material. The complex O 2 dynamics of the burrow environment also concurrently stimulated nitrification and coupled denitrification rates making the sediment an efficient sink for bioavailable nitrogen. Furthermore, bioturbation mediated a high efflux of dissolved phosphorus and silicate. The study documents a high spatial and temporal variation in benthic solute exchange with important implications for benthic turnover of organic carbon and nutrients. However, more long-term in situ investigations with like approaches are required to fully understand how environmental events and spatio-temporal variations interrelate to the overall biogeochemical functioning of coastal sediments.

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Section: Benthic Carbon and Nutrient Turnover In A Highly Irrigated Csupporting

confidence: 81%

Section: Benthic Carbon and Nutrient Turnover In A Highly Irrigated Cmentioning

confidence: 99%

Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

et al. 2016

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“…1 The lignin data was previously used as the biomarker for terrestrial OM in our studies to determine the fate of terrestrial OM in the lochs (Loh et al, 2008).…”

Section: Bulk Elemental and Isotope Analysesmentioning

confidence: 99%

“…2 The loss on ignition and bulk elemental results were previously used in Loh et al (2008) to determine the fate of terrestrial OM in the water column, during transportation down the lochs, and upon burial in the sediment.…”

Section: Loss On Ignition and Bulk Elemental Compositionmentioning

confidence: 99%

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Assessing the biodegradability of terrestrially-derived organic matter in Scottish sea loch sediments

Loh

Miller

Reeves

et al. 2008

Hydrol. Earth Syst. Sci.

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Abstract. Lignin oxidation products, oxygen uptake rates, molar organic carbon to nitrogen (OC/N) ratio (from bulk elemental analysis) and Rp values (from loss on ignition experiments, the ratio of the refractory to total organic matter, OM) were determined for sediments along transects of Loch Creran and Loch Etive. Lignin data indicated the importance of riverine inputs contributing to land-derived carbon in the lochs as total lignin ( , mg/100 mg organic carbon, OC) decreased from 0.69 to 0.45 and 0.70 to 0.29 from the head to outside of Loch Creran and Loch Etive, respectively. In addition, significant correlations of lignin content against total OM and OC (p<0.05) also suggested a distinct contribution of terrestrial OM to carbon pools in the lochs. The general trend of decreasing oxygen uptake rates from the head (20.8 mmole m −2 day −1 ) to mouth (9.4 mmole m −2 day −1 ) of Loch Creran indicates decomposition of OM. Biodegradability of the sedimentary OM was also characterized by the increase of Rp values from the head to mouth of the lochs: 0.40 to 0.80 in Loch Etive and 0.43 to 0.63 in Loch Creran. Furthermore, the molar OC/N ratio decreased from 11.2 to 6.4 in Loch Creran, and from 17.5 to 8.2 in Loch Etive. Derived rate constants for OM degradation were found to decrease from LC0 to LC1, and increase from RE5 to RE6. This work demonstrates that oxygen uptake rates, Rp values and molar OC/N ratio are able to serve as useful proxies to indicate the biodegradability of sedimentary OM.

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Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

Smeaton

Austin

2017

JGR Biogeosciences

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Fjords are recognized as globally important sites for the burial and long‐term storage of carbon (C) within sediments. The proximity of fjords to the terrestrial environment in combination with their geomorphology and hydrography results in the fjordic sediments being subsidized with organic carbon (OC) from the terrestrial environment. It has been well documented that terrestrial OC (OCterr) is an important component of coastal sediments, yet our understanding of the quantity of OCterr stored in these sediments remains poorly constrained. Utilizing Bayesian isotopic sediment fingerprinting techniques to the surface sediments of Loch Sunart, we estimate that 42.0 ± 10.1% of the OC is terrestrial in origin. Through combining these outputs with sedimentary OC stock estimates, we have calculated that the surface sediments (0–15 cm) hold 0.1 megaton (Mt) OCterr and estimate that the postglacial sediment held within the fjord contains 3.96 Mt OCterr. When these totals are compared to the quantity of OC stored in the adjacent terrestrial environment, it is clear that the fjord's catchment stores a greater amount of OCterr in the form of vegetation and soil. Though when normalized for area the results suggest that the marine sediments are a more effective long‐term store of OCterr than the adjacent terrestrial environment. This striking result highlights the importance of the terrestrial environment as a source of OC to the coastal ocean and that the OCterr subsidy to the marine sediments is a significant mechanism for the long‐term storage of OC in coastal marine sediments.

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The fate of terrestrial organic matter in two Scottish sea lochs

Cited by 32 publications

References 79 publications

Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

Assessing the biodegradability of terrestrially-derived organic matter in Scottish sea loch sediments

Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

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